The present invention relates to elastic metallized decorative moldings composed of a modified polyurethane resin as a substrate coated on the surface thereof with a metallized layer. More particularly, the present invention relates to elastic metallized decorative molded articles useful as impact-absorbing materials in which a metallized layer is coated on the surface of an elastic substrate composed of a specific plastic polyurethane resin modified with an AS or ABS resin in a specific proportion.
In recent years, elastic decorative moldings made of an elastic synthetic resin have been mounted in place of rubber moldings on bumpers and side exterior walls of motor vehicles for the purpose of not only protecting the motor vehicles from damage caused by external impact but also improving aesthetic value in appearance. Accordingly, resinous materials for such elastic decorative resin moldings are naturally required to be excellent in impact-resistance, self-redintegration in shape and size, strength, abrasion resistance and the like properties. As motor vehicles are exposed under severe weathering conditions, the resinous materials are also required, as a matter of course, to be satisfactory in heat-resistance and cold-resistance. From the economical point of view, the resinous materials are further required to be suited for processing by injection molding or extrusion molding operations generally adopted as advantageous means for mass production.
Hitherto used elastic decorative moldings having metallic appearance for motor vehicles are (A) soft polyvinyl chloride moldings provided on the surface thereof with a multi-layer film of polyvinyl fluoride (top protective layer)-aluminum vapor deposited on polyethylene terephthalate (metallized layer)-polyvinyl chloride (undercoat layer) or with a thin layer of stainless steel by the aid of a binder or (B) vulcanized rubber moldings provided on the surface thereof with a thin metal layer by vacuum deposition. However, these prior art products have many drawbacks in practical use. In case of the product (A), disfigurement tends to remain on the surface when the product is significantly deformed, and moreover, either of cold-resistance and heat-resistance of the substrate becomes poor according to the proportion of a plasticizer incorporated into the polyvinyl chloride substrate. In case of the product (B), vacuum deposition of a metal is disturbed considerably by evaporation of processing oils, plasticizers and the like ingredients incorporated into the vulcanized rubber substrate so that the luster of the metal deposited is lost or adhesiveness of the metal film to the substrate becomes extremely poor. For overcoming these drawbacks, an improved process is proposed wherein melamine, alkyd resin or the like paint is applied onto the surface of the rubber substrate to form a migration-preventing layer by which evaporation of ingredients incorporated into the substrate is prevented. However, the products obtained according to this improved process still have shortcomings, in that the metal film is cracked or delaminated on deformation of the products because of poor adhesiveness between the substrate and the migration-preventing layer or poor flexibility of the migration-preventing layer. Thus, polyvinyl chloride, natural and synthetic rubbers are found to be unsatisfactory as the substrate for elastic decorative moldings for motor vehicles.
On the other hand, other elastic resins such as polyurethane alone or as a mixture with ABS or AS resin come into question as the elastic substrate. However, known compositions comprised of polyurethane and ABS or AS resin disclosed in Japanese Patent Publn. Nos. 19492/61 and 659/71 are also found to be unsatisfactory as the substrate for elastic decorative moldings for automobiles since these compositions are extremely poor in at least one of the several severe conditions as required for motor vehicles. Thus, an important key to overcoming the drawbacks of the prior art elastic decorative moldings is to use a special resinous material as substrate which can satisfy all of the above mentioned necessary physical properties. Hence, there is a great demand for development of a new resinous material which satisfies the severe conditions as required for motor vehicles when it is used as substrate for elastic decorative moldings.